Prospective inter-relationships between late adolescent personality and major depressive disorder in early adulthood.

BACKGROUND: A well-established body of literature demonstrates concurrent associations between personality traits and major depressive disorder (MDD), but there have been relatively few investigations of their dynamic interplay over time.
METHOD: Prospective inter-relationships between late-adolescent personality and MDD in early adulthood were examined in a community sample of male and female twins from the Minnesota Twin Family Study (MTFS; n = 1252). Participants were classified into naturally occurring MDD groups based on the timing (adolescent versus adult onset) and course (chronic/recurrent versus remitting) of MDD. MDD diagnoses were assessed at ages 17, 20, 24 and 29 years, and personality traits [negative emotionality (NEM), positive emotionality (PEM) and constraint (CON)] were assessed at ages 17, 24 and 29 years.
RESULTS: Multilevel modeling (MLM) analyses indicated that higher age-17 NEM was associated with the subsequent development of MDD, and any MDD, regardless of onset or course, was associated with higher NEM up to age 29. Moreover, the chronic/recurrent MDD groups failed to show the normative decrease in NEM from late adolescence to early adulthood. Lower age-17 PEM was also associated with the subsequent development of MDD but only among the chronic/recurrent MDD groups. Finally, the adolescent-onset MDD groups reported lower age-17 CON relative to the never-depressed and adult-onset MDD groups.
CONCLUSIONS: Taken together, the results speak to the role of personality traits for conferring risk for the onset of MDD in late adolescence and early adulthood, in addition to the pernicious implications of chronic/recurrent MDD, particularly when it onsets during adolescence, for adaptive personality development.